Islamic State (IS) fighters are making it more difficult for people to travel regionally among IS areas in northern Syria, activists and news reports say.

IS issued a new decree, which went into effect Monday, that requires residents of its de-facto capital Raqqa to get permission from IS's security offices for any travel between villages under IS control.

“In the past, people couldn't leave [IS] territory, but what's new this time is that they can't even leave their cities to other IS-held areas,” said Hussam Eesa of Raqqa Is Being Slaughtered Silently, an activist group that reports on IS activities in Raqqa and other parts of Syria.

As part of the new ruling, IS has established strict measures, setting up more security checkpoints in and outside Raqqa to prevent local residents from leaving the city.

“At least 40 families were stopped at different checkpoints in Raqqa [on Monday],” activist Eesa told VOA. Some members of those fleeing families were detained and transferred to IS jails in Raqqa, he said.

Syrian Democratic Forces fighters ride on a vehicle near Raqqa, Feb. 5, 2017. The U.S.-backed troops have made significant advances.

Turkish troops lead way

The tighter restrictions came as IS suffers from major battlefield setbacks on several fronts around Raqqa and in al-Bab, a key IS city that is likely to fall soon in a Turkish-led offensive.

“This [IS rule] isn't just about asserting its rule,” said Saeed Shlash, a Syrian journalist who currently lives in exile in Turkey. “This is about keeping civilians in Raqqa to use them as human shields when anti-IS forces bring the battle into the city.”

The U.S.-backed Syrian Democratic Forces (SDF) have made significant advances on IS, pushing toward the city from the north and west.

“On some fronts, our forces are now only 11 kilometers away from Raqqa,” Rojda Felat, an SDF commander, told VOA last week.

IS families on the move

As the battle nears Raqqa, IS has begun moving many families of its fighters from the city, activist Eesa said.

“Wives and children of [IS] fighters are being transported to other towns and villages in Raqqa's countryside,” Eesa's group reported Monday.

In recent weeks, IS has also intensified its crackdown on smugglers facilitating people's escape. The group executed two men last week for allegedly trafficking people out of Raqqa.

One of the men was an IS security official who would charge up to $200 for each person escaping Raqqa, according to multiple Syrian news websites.

Local sources estimate that more than 200,000 people live under IS rule in Raqqa, including thousands relocated there by IS from Iraq's Mosul and the ancient Syrian town of Palmyra.

IS also executed a man publicly last week for trafficking residents out of the embattled northern town of al-Bab, where Turkish-backed rebels have been assaulting IS fighters from several sides.

Turkish forces and members of the Free Syrian Army are seen on the outskirts of al-Bab, Feb. 4, 2017.

Militants leaving al-Bab

Turkish President Recep Tayyip Erdogan said that his troops and Syrian rebel forces have besieged al-Bab and that pushing out IS militants from there is “a matter of time.”

The U.N. has said that nearly 10,000 civilians are stranded in al-Bab as Turkish fighter jets bomb IS positions inside the city. Some of those who managed to flee al-Bab have ended up in Raqqa, giving IS more people to use as human shields.

“The more civilians IS has under its control in Raqqa, the better positioned it will be to use them as leverage in upcoming battles over the city,” said journalist Shlash.